Which definition best describes an interpreter in programming?

The definition that best describes an interpreter is one that explains its function of translating code one line at a time for immediate execution. An interpreter processes source code written in a high-level programming language and converts it into machine code at runtime, which allows for immediate execution of that code. This real-time translation is particularly useful for scripting languages and during the development phase, as it enables developers to test and debug their code without needing to compile the entire program first.

This real-time feedback loop can enhance productivity by allowing programmers to see results instantly. While it doesn't create a standalone executable file as a compiler would, it plays a key role in environments where interactive code execution is important, such as during software development and testing.

Other options detail different tools or processes involved in programming but do not accurately capture the essence of what an interpreter does.